Calculator



Oct. 1, 1929. R. L. ELLISON 1,729,714

CALCULATOR Filed Jan. 7, 1927 Patented 1, 1929 PATENT OFFICE ROBERT L. ELLISON, F WILLIAMSIOR'I, PENNSYLVANIA CALCULATOR Application filed January 7, 1927.

lfhis invention relates to calculators and has for its object the provision of a simple and easily manipulated device by the use of which the interest accruing through any 1 period may be easily ascertained without mental effort. The invention is illustrated in the accompanying drawing and will be hereinafter fully set forth.

In the drawing;

Figure 1 is a plan view of a device embodying the invention;

Figure 2 is a section.

In the apparatus illustrated, the numeral 1 indicates a casing or housing having a top plate 2 constructed with a radial slot 3 and a central opening a through which a shaft 5 is journaled. The front or exposed end of the shaft is equipped with a handle or knob 6 and its opposite end is pointed, as at 7, whereby it may rotate with minimum friction on the back or bottom plate of the easing. Within the casing a dial or chart 8 is carried by the shaft 5 in such position as to lie close to the face plate 2 and extend across the slot 3 therein. The chart or dial 8 is inscribed with a plurality of concentric circles 9 and radial lines 10 defining radial columns of blocks or regular spaces, the outermost circle being located inwardly from the edge of the dial and the radial lines stoppin at said circle whereby a clear margin 11 is provided on the dial. In the margin 11, at the heads of the several columns, are numerals, 12, running from 0 to and indicating days, the calculations being based on an allotment of thirty days to a month and the 0 column representing periods of months. On the face plate 2 at one side of the slot 3 in position to aline with the margin 11 of the dial is inscribed the word Days, a blanlt space under said word alining with the outermost circular row of blocks or spaces. Extending toward the centre of the plate alongside the slot 3, as shown at 13, are inscriptions aligning successively with respective rows of spaces or blocks and designating periods of from one to eleven months. In the outermost space or block of the column 1 is inscribed a number representing interest for one day on Serial No. 159,670.

one dollar at a given rate, six per cent being used in the illustrated example. In the outermost space of the 2 column is inscribed the amount of two days interest and the calculations are in this manner carried through the entire series of rows and colums. The amount which appears in the outermost row in the 30 column is also inscribed in the second row in the 0 column, this stepping being repeated for each thirtyday period so that the same sum which appears in any row in the 30 column also appears in the next inner row in the 0 column.

Assuming that it is desired to find the interest on $225 for twenty-one days, the dial is turned until the marginal number 21 appears in alinement with the word Days and the number then appearing in the slot 3 immediately under 21 gives the interest on $51 which, obviously, multiplied by 225 will give the amount desired. If the interest is for one month and twenty-one days, the number to be multiplied will be that appearing in the slot alined with the inscription 1 month.

The device is obviously simple, inexpensive, easily manipulated, and certain in result. It will, of course, be understood that dials may be furnished in any number, each dial containing calculations at a certain rate so that the dials may be used interchangeably and a desired range of operations accommodated.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent, is:

A calculator comprising a casing having a radial slot in the face plate, a shaft jour naled through the face plate of the casing at the end thereof. a handle member on the front end of the face plate, and a dial carried by the shaft within the casing close to the inner side of the face plate, the face plate having designations alongside the radial slot and the dial having a clear marginal portion and bearing upon its face radial lines and concentric circles defining radial columns and annular rows of blocks, the area and dimensions of each column being the same as the area and dimensions of the radial slot in the face plate there being progressive column designations in the marginal portion of the dial and numbers in the several blocks representing values which are functions of the marginal designations of the respective columns, the number in any block in the last radial column being the same as the number in the first radial column in the block in the next adjacent inner row of blocks.

In testimony whereof, I have signed this specification.

ROBERT L. ELLISON. 

